1. Field of the Invention
The present invention is concerned with an improvement in or relating to a slurry seal designed to seal up a fluid containing much slurry.
2. Prior Art
Heretofore, a prior art slurry pump used for pumping up muddy water or the like has been provided as a shaft sealing means with such a slurry seal as illustrated in FIG. 2.
More specifically, the illustrated slurry seal is designed such that a stationary seal ring 103 fixed through a packing 102 over a flange 101 located on the side of a pump casing and a rotary seal ring 108 held through a packing 107 over a seal cover 106 fixed to an end of a sleeve 105 mounted over a shaft 104 are brought into closely sliding contact with each other on their axially opposite sliding surfaces 103a and 108a, thereby preventing leakage of a fluid sealed up in a certain space S leading to the impeller side, not illustrated, from around the shaft.
The flange 101 is provided with a quenching hole 109 communicating with the side of the packing 102 attached over the stationary seal ring 103, which is opposite to the space S. Between the inner faces of both seal rings 103 and 108 and the outer face of the sleeve 105 mounted over the shaft 104, there is a baffle sleeve 110 fixed at one end to the inner end of the flange 101 and having the other end terminating at a position located in the rear of the rotary seal ring 108. Quenching water, supplied through the quenching hole 109 to the side 113 of the packing 102 which is opposite to the space S, flows through a gap 111 between the baffle sleeve 110 and both rings 103 and 108 toward the seal cover 106, whence it is discharged into the atmosphere A through a gap 112 between the baffle sleeve 110 and the sleeve 105.
A problem with the above-mentioned shaft seal, however, is that as the packing 107 for the rotary seal ring 108 rotates with said seal ring 108 and seal cover 106 and moves relative to the fluid contained in the space S and coming into contact with its surface, it is prone to erode vigorously by slurries of earth and sand, dust coal or the like contained in large amounts in the fluid. The packing 107 also serves as a spring to an axial movement of the rotary seal ring 6 by a reactionary force of compression, applying the pressure required for sealing-up to the sliding surfaces 103a and 108a. However, as such erosion by slurries as mentioned above proceeds, some adverse influence is produced on the loads applied to the sliding surfaces 103a and 108b with a fear of causing a premature drop in performance of the shaft seal.
In view of the foregoing, the present invention seeks to prevent premature erosion by slurry of the packing located around the rotary seal ring.